Identification of A Novel Chitinase from <i>Myxococcus landrumensis</i> with Substrate Promiscuity to Produce Various Aminooligosaccharides

This study obtained a novel chitinase gene (<i>MlChi54</i>) from <i>Myxococcus landrumensis</i>. <i>MlChi54</i> has been successfully expressed, and the enzyme exhibited a chitinase activity of 10 U mg^-1. Furthermore, MlChi54 demonstrated hydrolytic activity toward chitosan (2.6 U mg^-1), exhibiting substrate promiscuity. Various aminooligosaccharides were produced by MlChi54 hydrolysis of chitosan (75% deacetylation). High-performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS) analyses were used to demonstrate that GlcNAc, (GlcNAc)₂, and GlcNAc-β-1,4-GlcN-β-1,4-GlcNAc were the predominant components. A comparative structural analysis of three chitinases revealed that the catalytic groove of MlChi54 exhibited a negative electrostatic potential, while the distinctive groove architecture promoted enzymatic activity against chitosan. Furthermore, molecular dynamics (MD) simulations indicated that MlChi54 exhibited relatively stable conformations with three distinct deacetylated chitosan complexes. These unique enzymatic properties and structural characteristics may make MlChi54 a good candidate for the production of various aminooligosaccharides in the food, pharmaceutical, and agricultural industries.